This invention relates to a ring binder mechanism for retaining loose-leaf pages, and in particular to an improved mechanism for opening and closing ring members and for readily and securely locking closed ring members together.
A ring binder mechanism retains loose-leaf pages, such as hole-punched pages, in a file or notebook. It has ring members for retaining the pages. The ring members may be selectively opened to add or remove pages or closed to retain pages while allowing them to be moved along the ring members. The ring members mount on two adjacent hinge plates that join together about a pivot axis for pivoting movement within an elongated housing. The housing loosely holds the hinge plates so they may pivot relative to the housing. The undeformed housing is slightly narrower than the joined hinge plates when the hinge plates are in a coplanar position (180°). So as the hinge plates pivot through this position, they deform the resilient housing and cause a spring force in the housing urging the hinge plates to pivot away from the coplanar position either opening or closing the ring members. Thus, when the ring members are closed the spring force resists hinge plate movement and clamps the ring members together. Similarly, when the ring members are open, the spring force holds them apart. An operator may typically overcome this force by manually pulling the ring members apart or pushing them together. Levers may also be provided on both ends of the binder for moving the ring members between the open and closed positions.
One drawback to these typical ring binder mechanisms is that when the ring members close, the housing's spring force snaps them together rapidly and with a force that might cause fingers to be pinched between the ring members. The substantial spring force required to keep the ring members closed also makes pivoting the hinge plates through the coplanar position (180°) difficult so that it is hard to both open and close the ring members. Another drawback is that when the ring members are closed, they do not positively lock together. So if the mechanism is accidentally dropped, the ring members may unintentionally open. Still another drawback is that over time the housing may begin to permanently deform, reducing its ability to uniformly clamp the ring members together and possibly causing uneven movements or gaps between closed ring members.
To address these concerns, some ring binder mechanisms include a control slide attached directly to the lever. These control slides have inclined cam surfaces that project through openings in the hinge plates for rigidly controlling the hinge plates' pivoting motion both when opening and closing the ring members. Examples of these types of mechanisms are shown in U.S. Pat. Nos. 4,566,817, 4,571,108, and 6,276,862 and in U.K. Pat. No. 2,292,343. Some of these cam surfaces have a stop for blocking the hinge plates' pivoting motion when the ring members are closed and for locking the closed ring members together. These mechanisms require the operator to move the lever to lock the rings closed. The operator must manually move the lever to move the control slide stops into position to block the hinge plates from pivoting. Failure to do this could result in the rings inadvertently opening and pages falling out. Any solution to this issue should be made so as to keep the construction simple and economic, and avoid causing the rings to snap closed.
Accordingly, there is a need for an efficient ring binder mechanism that readily locks when ring members close for retaining loose-leaf pages and has ring members that easily open and close.